In this work, we provide experimental measurements of the flow above a non-magnetic, absorbing boundary in a magnetized plasma. Measurements are taken as a function of the angle between the background magnetic field and the boundary normal. The measurements are compared to computational predictions for oblique magnetic fields based on Chodura's model. Ion flow measurements were obtained with laser induced fluorescence and the presheath potential structure was measured with an emissive probe. The ions were found to accelerate to nearly 30% of the sound speed parallel to the boundary at oblique angles of the magnetic field (∼80°) and the ion speed at the electrostatic sheath edge was found to decrease with angle. The edge of the magnetic presheath has been experimentally determined based on the appearance of the drift and is found to be independent of the angle of the magnetic field. We also demonstrate that laser induced fluorescence is suitable as a non-perturbative diagnostic to measure the electric field in a magnetized sheath.
References
1.
R.
Chodura
, “Plasma–wall transition in an oblique magnetic field
,” Phys. Fluids
25
, 1628
–1633
(1982
).2.
I. Y.
Senichenkov
, E.
Kaveeva
, E.
Sytova
, V.
Rozhansky
, S.
Voskoboynikov
, I. Y.
Veselova
, D.
Coster
, X.
Bonnin
, and F.
Reimold
, “On mechanisms of impurity leakage and retention in the tokamak divertor
,” Plasma Phys. Controlled Fusion
61
, 045013
(2019
).3.
P.
Stangeby
and A.
Chankin
, “The ion velocity (Bohm–Chodura) boundary condition at the entrance to the magnetic presheath in the presence of diamagnetic and E × B drifts in the scrape-off layer
,” Phys. Plasmas
2
, 707
–715
(1995
).4.
P.
Stangeby
and A.
Chankin
, “Simple models for the radial and poloidal E × B drifts in the scrape-off layer of a divertor tokamak: Effects on in/out asymmetries
,” Nucl. Fusion
36
, 839
(1996
).5.
J.
Loizu
, P.
Ricci
, F.
Halpern
, and S.
Jolliet
, “Boundary conditions for plasma fluid models at the magnetic presheath entrance
,” Phys. Plasmas
19
, 122307
(2012
).6.
J.
Loizu
, J.
Morales
, F.
Halpern
, P.
Ricci
, and P.
Paruta
, “Scrape-off-layer current loops and floating potential in limited tokamak plasmas
,” J. Plasma Phys.
83
, 575830601
(2017
).7.
D.
Tskhakaya
, “One-dimensional plasma sheath model in front of the divertor plates
,” Plasma Phys. Controlled Fusion
59
, 114001
(2017
).8.
L.
Popova
, G.
Kamberov
, T.
Nikolov
, P.
Marinov
, and D.
Mitev
, “Method for simulation of particle recombination in SOL plasma
,” Bulg. J. Phys
32
, 263
–271
(2005
).9.
A.
Geraldini
, F. I.
Parra
, and F.
Militello
, “Gyrokinetic treatment of a grazing angle magnetic presheath
,” Plasma Phys. Controlled Fusion
59
, 025015
(2017
).10.
F. D.
Halpern
, P.
Ricci
, S.
Jolliet
, J.
Loizu
, J.
Morales
, A.
Mosetto
, F.
Musil
, F.
Riva
, T.-M.
Tran
, and C.
Wersal
, “The GBS code for tokamak scrape-off layer simulations
,” J. Comput. Phys.
315
, 388
–408
(2016
).11.
K.-U.
Riemann
, “Theory of the collisional presheath in an oblique magnetic field
,” Phys. Plasmas
1
, 552
–558
(1994
).12.
E.
Ahedo
and D.
Carralero
, “Model of a source-driven plasma interacting with a wall in an oblique magnetic field
,” Phys. Plasmas
16
, 043506
(2009
).13.
K.-U.
Riemann
, “The Bohm criterion and sheath formation
,” J. Phys. D
24
, 493
(1991
).14.
S.-B.
Wang
and A. E.
Wendt
, “Sheath thickness evaluation for collisionless or weakly collisional bounded plasmas
,” IEEE Trans. Plasma Sci.
27
, 1358
–1365
(1999
).15.
E.
Ahedo
, “Structure of the plasma-wall interaction in an oblique magnetic field
,” Phys. Plasmas
4
, 4419
–4430
(1997
).16.
P.
Stangeby
, “The Bohm–Chodura plasma sheath criterion
,” Phys. Plasmas
2
, 702
–706
(1995
).17.
P.
Stangeby
, “The Chodura sheath for angles of a few degrees between the magnetic field and the surface of divertor targets and limiters
,” Nucl. Fusion
52
, 083012
(2012
).18.
M. U.
Siddiqui
, C. D.
Jackson
, J. F.
Kim
, and N.
Hershkowitz
, “Direct measurements of ion dynamics in collisional magnetic presheaths
,” Phys. Plasmas
21
, 102103
(2014
).19.
M. U.
Siddiqui
, D. S.
Thompson
, C. D.
Jackson
, J. F.
Kim
, N.
Hershkowitz
, and E. E.
Scime
, “Models, assumptions, and experimental tests of flows near boundaries in magnetized plasmas
,” Phys. Plasmas
23
, 057101
(2016
).20.
D. S.
Thompson
, R.
Khaziev
, M.
Fortney-Henriquez
, S.
Keniley
, E. E.
Scime
, and D.
Curreli
, “Three-dimensional cross-field flows at the plasma-material interface in an oblique magnetic field
,” Phys. Plasmas
27
, 073511
(2020
).21.
E. E.
Scime
, P. A.
Keiter
, M. M.
Balkey
, J. L.
Kline
, X.
Sun
, A. M.
Keesee
, R. A.
Hardin
, I. A.
Biloiu
, S.
Houshmandyar
, S. C.
Thakur
, J.
Carr
, M.
Galante
, D.
McCarren
, and S.
Sears
, “The hot helicon experiment (HELIX) and the large experiment on instabilities and anisotropy (LEIA)
,” J. Plasma Phys.
81
, 345810103
(2015
).22.
E.
Scime
, R.
Hardin
, C.
Biloiu
, A.
Keesee
, and X.
Sun
, “Flow, flow shear, and related profiles in helicon plasmas
,” Phys. Plasmas
14
, 043505
(2007
).23.
F.
Chu
, R.
Hood
, and F.
Skiff
, “Measurement of wave-particle interaction and metastable lifetime using laser-induced fluorescence
,” Phys. Plasmas
26
, 042111
(2019
).24.
Y.-K.
Lee
and C.-W.
Chung
, “Ionization in inductively coupled argon plasmas studied by optical emission spectroscopy
,” J. Appl. Phys.
109
, 013306
(2011
).25.
X.
Sun
, C.
Biloiu
, R.
Hardin
, and E. E.
Scime
, “Parallel velocity and temperature of argon ions in an expanding, helicon source driven plasma
,” Plasma Sources Sci. Technol.
13
, 359
(2004
).26.
G.
Severn
, D.
Edrich
, and R.
McWilliams
, “Argon ion laser-induced fluorescence with diode lasers
,” Rev. Sci. Instrum.
69
, 10
–15
(1998
).27.
R.
Bovin
, “Study of the different line broadening mechanisms for the laser induced fluorescence diagnostic of the HELIX and LEIA plasmas
,” Technical Report No. PL-039
(West Virginia University
, 1998
).28.
R.
Boivin
, “Study of the different line broadening mechanisms for the laser induced fluorescence diagnostic of the HELIX and LEIA plasmas
,” Technical Report No. PL-039
(West Virginia University Plasma Physics Lab
, Morgantown, WV
, 2000
).29.
V.
Demidov
, S. V.
Ratynskaia
, and K.
Rypdal
, “Electric probes for plasmas: The link between theory and instrument
,” Rev. Sci. Instrum.
73
, 3409
–3439
(2002
).30.
V.
Godyak
and V.
Demidov
, “Probe measurements of electron-energy distributions in plasmas: What can we measure and how can we achieve reliable results?
,” J. Phys. D
44
, 233001
(2011
).31.
J.
Sheehan
and N.
Hershkowitz
, “Emissive probes
,” Plasma Sources Sci. Technol.
20
, 063001
(2011
).32.
J.
Sheehan
, Y.
Raitses
, N.
Hershkowitz
, I.
Kaganovich
, and N. J.
Fisch
, “A comparison of emissive probe techniques for electric potential measurements in a complex plasma
,” Phys. Plasmas
18
, 073501
(2011
).33.
J.
Kline
, E.
Scime
, R.
Boivin
, A.
Keesee
, X.
Sun
, and V.
Mikhailenko
, “RF absorption and ion heating in helicon sources
,” Phys. Rev. Lett.
88
, 195002
(2002
).34.
L.
Oksuz
and N.
Hershkowitz
, “Plasma, presheath, collisional sheath and collisionless sheath potential profiles in weakly ionized, weakly collisional plasma
,” Plasma Sources Sci. Technol.
14
, 201
(2005
).35.
B.
Singha
, A.
Sarma
, and J.
Chutia
, “Experimental observation of sheath and magnetic presheath over an oblique metallic plate in the presence of a magnetic field
,” Phys. Plasmas
9
, 683
–690
(2002
).36.
L.
Oksuz
and N.
Hershkowitz
, “First experimental measurements of the plasma potential throughout the presheath and sheath at a boundary in a weakly collisional plasma
,” Phys. Rev. Lett.
89
, 145001
(2002
).37.
N. S.
Krasheninnikova
, X.
Tang
, and V. S.
Roytershteyn
, “Scaling of the plasma sheath in a magnetic field parallel to the wall
,” Phys. Plasmas
17
, 057103
(2010
).© 2021 Author(s). Published under an exclusive license by AIP Publishing.
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